1. Field of Invention
The present invention relates to a composite type thin film magnetic head constructed by stacking an inductive type writing magnetic transducing element and a magnetoresistive type reading magnetic transducing element on a substrate.
2. Description of Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly. A composite type thin film magnetic head is constructed by stacking an inductive type thin film magnetic head intended for writing and a magnetoresistive type thin film magnetic head intended for reading on a substrate, and has been practically used. In general, as a reading magnetoresistive element, an element utilizing anisotropic magnetoresistive (AMR) effect has been used so far, but there has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than that of the normal anisotropic magnetoresistive effect by several times. In the present specification, elements exhibiting a magnetoresistive effect such as AMR and GMR reproducing elements are termed as a magnetoresistive reproducing element or MR reproducing element.
By using the AMR reproducing element, a very high surface recording density of several gigabits/inch2 has been realized, and a surface recording density can be further increased by using the GMR element. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity of more than 10 gigabytes.
A height (MR Height: MRH) of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. The MR height MRH is a distance measured from an air bearing surface on which one edge of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, the performance of the recording magnetic head is also required to be improved in accordance with the improvement of the performance of the reproducing magnetic head. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium as high as possible. For this purpose, a width of a write gap at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head.
One of factors determining the performance of the inductive type thin film writing magnetic head is a throat height TH. This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. The reduction of this throat height is also decided by an amount of polishing the air bearing surface.
Therefore, in order to improve the performance of the composite type thin film magnetic head having the writing inductive type thin film magnetic head and reading magnetoresistive type thin film magnetic head stacked one on the other, it is important that the recording inductive type thin film magnetic head and reproducing magnetoresistive type thin film magnetic head are formed with a good balance.
FIGS. 1A-9B show successive steps for manufacturing a conventional standard thin film magnetic head, in these drawings A depicts a cross-sectional view of a substantial portion of the head and B represent a cross sectional view of a pole portion. Moreover, FIGS. 10-12 are a cross sectional view of a substantial portion of the completed thin film magnetic head, a cross sectional view of the pole portion, and a plan view of the substantial portion of the thin film magnetic head, respectively. It should be noted that the thin film magnetic head is of a composite type in which the inductive type thin film magnetic head for writing is stacked on the reproducing MR element.
First of all, as shown in FIGS. 1A and B, an insulating layer 2 consisting of, for example alumina (Al2O3) is deposited on a substance 1 made of a non-magnetic and electrically insulating material such as AlTiC and having a thickness of about 5-10 xcexcm. Next, as shown in FIGS. 2A and B, a first magnetic layer 3 which constitutes one of magnetic shields protecting the MR reproduction element of the reproducing head from the influence of an external magnetic field, is formed with a thickness of 3 xcexcm. Afterwards, as shown in FIGS. 3A and B, after depositing an insulating layer 4 of thickness 100-150 nm serving as a shield gap by spattering alumina, a magnetoresistive layer 5 made of a material having the magnetoresistive effect and constituting the MR reproduction element is formed on the shield gap layer with a thickness of several tens nano meters and is then shaped into a given pattern by the highly precise mask alignment.
Then, as shown in FIGS. 4A and B, an insulating layer 6 is formed such that the magnetoresistive layer 5 is embedded within the insulating layers 4 and 6.
Next, as shown in FIGS. 5A and B, a second magnetic layer 7 made of a permalloy is formed with a film thickness of 3 xcexcm. This second magnetic layer 7 has not only the function of the upper shield layer which magnetically shields the MR reproduction element together with the above described lower shield layer 3, but also has the function of one of poles of the writing thin film magnetic head.
Then, after forming a write gap layer 7 made of a non-magnetic material such as alumina and having a thickness of about 200 nm on the second magnetic layer 7, a pole chip 9 made of a material having a high saturation magnetic flux density such as permalloy (Ni:50 wt %, Fe:50 wt %) and nitride iron (FeN) is formed with a desired shape by the highly precise mask alignment. A track width is determined by a width W of the pole chip 9. Therefore, in order to realize a high surface recording density, it is necessary to decrease the width W. In this case, a dummy pattern 9xe2x80x2 for coupling the bottom pole (first magnetic layer) with the top pole (third magnetic layer) is formed simultaneously. Then, a through-hole can be easily formed by polishing or chemical mechanical polishing (CMP).
In order to prevent an effective width of writing track from being widened, that is, in order to prevent a magnetic flux from being spread at the bottom pole upon the data writing, portions of the gap layer 8 and second magnetic layer 7 constituting the other pole surrounding the pole chip 9 are etched by an ion beam etching such as ion milling. The structure after this process is shown in FIGS. 5A and B. This structure is called a trim structure and this portion serves as a pole portion of the first magnetic layer.
Next, as shown in FIGS. 6A and B, after forming an insulating layer, for example alumina film 10 with a thickness of about 3 xcexcm, the whole surface is flattened by, for instance CMP. Subsequently, after forming an electrically insulating photoresist layer 11 into a given pattern by the mask alignment of high precision, a first layer thin film coil 12 made of, for instance copper is formed on the photoresist layer 11. Continuously, as shown in FIGS. 7A and B, after forming an electrically insulating photoresist layer 13 on the thin film coil 12 by the highly precise mask alignment, the photoresist layer is sintered at a temperature of, for example 250-300xc2x0 C.
In addition, as shown in FIGS. 8A and B, a second layer thin film coil 14 is formed on the flattened surface of the photoresist layer 13. Next, after forming a photoresist layer 15 on the second layer thin film coil 14 with the highly precise mask alignment, the photoresist layer is flattened by performing the sintering process at a temperature of, for example 250xc2x0 C. As described above, the reason why the photoresist layers 11, 13 and 15 are formed by the highly precise mask alignment process, is that the throat height and MR height are defined on the basis of a position of the edges of the photoresist layers on a side of the pole portion.
Next, as shown in FIGS. 9A and B, a third magnetic layer 16 made of, for example a permalloy and having a thickness of 3 xcexcm is selectively formed on the pole chip 9 and photoresist layers 11, 13 and 15 in accordance with a desired pattern.
This third magnetic layer 16 is coupled with the first magnetic layer 7 at a rear position remote from the pole portion through the dummy pattern 9xe2x80x2, and the thin film coil 12, 14 passes through a closed magnetic circuit composed of the second magnetic layer, pole chip and third magnetic layer. Furthermore, an overcoat layer 17 made of alumina is deposited on the exposed surface of the third magnetic layer 16.
Finally, a side surface of an assembly at which the magnetoresistive layer 5 and gap layer 8 are formed is polished to form an air bearing surface (ABS) 18 which is to be opposed to the magnetic record medium. During the formation of the air bearing surface 18, the magnetoresistive layer 5 is also ground to obtain a MR reproduction element 19. In this way, the above described throat height TH and the MR height MRH are determined. This condition is shown in FIG. 10. In an actual thin film magnetic head, electric conductors and contact pads for performing the electrical connection to the thin film coils 12, 14 and MR reproduction element 19 are formed, but they are not shown in the drawings.
As shown in FIG. 10, an angle xcex8 (apex Angle) between a line S connecting side corners of the photoresist layers 11,13,15 for isolating the thin film coils 12,14 and the upper surface of the third magnetic layers 16 is an important factor for determining the performance of the thin film magnetic head together with the above described throat height TH and MR height.
Moreover, as shown in the plan view of FIG. 12, the width W of the pole chip 9 and a pole portion 20 of the third magnetic layer 16 is small. Since the width of the track recorded on the magnetic record medium is defined by this width W it is necessary to narrow this width as small as possible in order to achieve a high surface recording density. It should be noted that in this figure, for the sake of convenience, the thin film coils 12, 14 are shown concentrically.
In the method of manufacturing the conventional thin film magnetic head, there is a problem that after forming the thin film coil, the top pole could not be formed precisely on the protruded coil section covered with the insulating photoresist especially along the inclined surface (apex).
That is to say, in the known method, the third magnetic layer is formed by first plating a magnetic material such as permalloy on the mountain shaped coil with a height of about 7-10 xcexcm, by applying the photoresist with a thickness of 3-4 xcexcm, and by shaping the magnetic layer into a given pattern by means of the photolithography technology. Now it is assumed that the photoresist formed on the protruded coil portion into a given pattern should have a thickness of 3 xcexcm or more, a thickness of the photoresist at a bottom or root of the inclined portion would amount to about 8-10 xcexcm. On the one hand, the third magnetic layer formed on the protruded coil portion having a height of about 10 xcexcm as well as on the write gap layer formed on the flat surface should have a narrow portion in the vicinity of the edges of the insulating photoresist layers (for instance layers 11 and 13 in FIGS. 7A and B) in order to realize a narrow track width. Therefore, it is necessary to form the pattern having a width of 1 xcexcm by using the photoresist film having a large thickness of 8-10 xcexcm.
However, it is extremely difficult to form the photoresist film having a thickness of 8-10 xcexcm into a pattern having a width of about 1 xcexcm, because upon the light exposure in the photolithography, a pattern deformation might occur due to reflection of light and resolution is reduced due to the thick photoresist layer. In this manner, it is extremely difficult to form a top pole defining precisely a narrow track width by patterning. Then, as is shown in the above explained conventional thin film magnetic head, in order to write data by means of the pole chip capable of forming the narrow track width, after forming the pole chip, the top pole is formed to be connected to the pole chip. In other words, in order to solve the above problem, a divided structure is adopted, that is, the pole chip for determining the track width and the third magnetic layer for introducing the magnetic flux.
However, the known thin film magnetic head, particularly the recording head formed as in the above manner still has the following problems.
(1) Since a positional relation between the pole chip 9 and the third magnetic layer 16 is determined by the alignment of the photoresist layer, a center line of the pole chip viewed from the air bearing surface might deviate largely from a center line of the third magnetic layer, and thus the magnetic flux might leak. Then, the data writing might be carried out by means of the magnetic flux leaked from the third magnetic layer, and the effective track width might be increased and data might be erroneously recorded on an adjacent track. In order to avoid such a problem, it is necessary to increase a distance between successive tracks. Then, the surface recording density could not be improved.
(2) Since the pole chip 9 having a narrow width is brought into contact with the wider third magnetic layer 16 at right angles, the magnetic flux is liable to be saturated at the contact portion, and therefore a satisfactorily high writing characteristic (Flux Rise Time) could not be obtained.
(3) The throat height TH and MR height are determined by taking a position of the edge of the insulating layer isolating the thin film coil on a side of the pole portion as a reference position, but the insulating layer is usually made of an electrically insulating organic photoresist layer and is liable to be deformed by heat. During the formation of the thin film coil, the insulating layer might be deformed by the heating treatment at about 250xc2x0 C., and a pattern size of the insulating layer changes, and the throat height TH and MR height might be deviated from desired design values.
(4) In the reading thin film magnetic head including the magnetoresistive element, it is advantage to use GMR element having a higher sensitivity, but the reading sensitivity of the GMR element degrades by the heating treatment at about 250xc2x0 C. for the photoresist layer during the formation of the thin film coil of the inductive type thin film magnetic head.
(5) The high sensitivity GMR element has such a structure that different kinds of very thin layers of thickness 1-5 nm are stacked on each other. Thus, during many steps which are required to complete the composite type thin film magnetic head after the formation of the GMR element, the MR element might be destroyed by electrostatic charge during the handling, and therefore a manufacturing yield might be disadvantageously decreased.
(6) At a nearly finishing stage of the mass production process of the composite type thin film magnetic head, the thick alumina film having a thickness not less than 30-40 xcexcm is formed as the overcoat layer for protecting the head and stabilizing the quality. Due to this thick layer, the substrate is liable to be bent. Furthermore, there might be produced many particles during the spattering process. Consequently characteristics of the magnetic head are degraded and defective magnetic heads might be produced. Moreover the formation of the thick alumina film by spattering requires a long time up to 15 hours or more, and therefore the throughput is extremely decreased. Furthermore, the etching process for exposing the contact pads connected to the magnetoresistive element via the electrode pattern takes a disadvantageously long time.
(7) In the composite type thin film magnetic head, the performance of the thin film magnetic head is mainly determined by the width and MR height of the magnetoresistive element of the magnetoresistive type thin film magnetic head, and by the width of the magnetic pole, throat height and NLTS (Non-Linear Transition Shift) of the inductive type thin film magnetic head. Therefore; demands of users are focused to these parameters. For example, the width of the magnetoresistive element may be designated by users as particular specifications. Since this dimension is determined at an early stage in the manufacturing process of the conventional composite type thin film magnetic head, a time from an order to a supply of products, i.e. the cycle time is prolonged, and sometimes amounts to 30-40 days.
It is an object of the present invention to provide a composite type thin film magnetic head and a method of manufacturing the same, in which various problems of the above mentioned known composite type thin film magnetic head and the known method of manufacturing the same can be solved or at least mitigated.
It is another object of the invention to provide a common unit for composite type thin film magnetic head which can be commonly used for composite type thin film heads having various characteristics.
According to the invention, a composite type thin film magnetic head in which a magnetoresistive type thin film magnetic head for reading and an inductive type thin film magnetic head for writing are supported by a substrate in a stacked fashion, comprises:
a substrate having a recessed portion formed in one surface thereof;
a first magnetic layer constituting one of shields for the magnetoresistive type thin film magnetic head and extending along said surface of the substrate from an end surface forming an air bearing surface to a vicinity of an edge of said recessed portion or to an inner surface of the recessed portion beyond the edge thereof;
a second magnetic layer constituting a part of one of poles for the inductive type thin film magnetic head and extending over a part of the inner surface of the recessed portion such that the second magnetic layer is magnetically separated from the first magnetic layer;
a thin film coil of the inductive type thin film magnetic head, at least a part of said thin film coil being formed within said recessed portion in an electrically isolated manner by an insulating film;
a magnetoresistive element arranged within a shield gap layer in an electrically and magnetically separated manner, said shield gap layer extending along a surface of said first magnetic layer opposite to the substrate;
a third magnetic layer constituting the other shield for the magnetoresistive type thin film magnetic head and extending along a surface of said shield gap layer opposite to the substrate, said third magnetic layer being coupled with said second magnetic layer formed within said recessed portion to constitute a rest of said one of poles of the inductive type thin film magnetic head;
a write gap layer extending at least along a surface of the third magnetic layer opposite to the substrate; and
a fourth magnetic layer constituting the other pole of the inductive type thin film magnetic head, extending along a surface of said write gap layer opposite to the substrate to be opposed to said third magnetic layer and being coupled with said second magnetic layer at a rear position remote from the air bearing surface.
According to the invention, a method of manufacturing a composite type thin film magnetic head in which a magnetoresistive type thin film magnetic head for reading and an inductive type thin film magnetic head for writing are supported by a substrate in a stacked fashion, comprises:
the step of forming a recessed portion in a surface of the substrate;
the step of forming a first magnetic layer constituting one of shields for the magnetoresistive type thin film magnetic head such that the first magnetic layer extends along the surface of the substrate from an end surface forming an air bearing surface to a vicinity of an edge of the recessed portion;
the step of forming a second magnetic layer constituting a part of one of poles for the inductive type thin film magnetic head such that the second magnetic layer extends along a part of an inner surface of the recessed portion in a magnetically isolated manner from the first magnetic layer;
the step of forming at least a part of a thin film coil for the inductive type thin film magnetic head within the recessed portion such that the thin film coil is isolated by an insulating layer;
the step of forming a magnetoresistive element along the surface of the first magnetic layer such that the magnetoresistive element extends in an electrically insulated and magnetically isolated manner;
the step of forming a third magnetic layer constituting the other shield for the magnetoresistive type thin film magnetic head such that the third magnetic layer extends along the magnetoresistive element and is coupled with said second magnetic layer formed within said recessed portion to constitute the remaining part of said one of poles for the inductive type thin film magnetic head;
the step of forming a write gap layer such that the write gap layer extends along at least a surface of the third magnetic layer;
the step of forming a fourth magnetic layer along a surface of the write gap layer such that the fourth magnetic layer is opposed to said third magnetic layer and is magnetically coupled with said second magnetic layer at a rear position remote from the air bearing surface to constitute the other pole for the inductive type thin film magnetic head; and
the step of polishing the air bearing surface.
Furthermore, according to the invention, a method of manufacturing a composite type thin film magnetic head in which a magnetoresistive type thin film magnetic head for reading and an inductive type thin film magnetic head for writing are supported by a substrate in a stacked fashion, comprises:
the step of manufacturing and stocking, on a large scale, common units commonly usable for composite type thin film magnetic heads having various characteristics, each of said common units including a substrate having a recessed portion formed therein, a first magnetic layer constituting one of shields for the magnetoresistive type thin film magnetic head and extending along a surface of the substrate from an end surface constituting an air bearing surface at least to a vicinity of an edge of said recessed portion, a second magnetic layer constituting a part of one of poles for the inductive type thin film magnetic head and extending over a part of an inner surface of the recessed portion such that the second magnetic layer is magnetically separated from the first magnetic layer, and at least a part of a thin film coil of the inductive type thin film magnetic head formed within said recessed portion in an electrically isolated manner by an insulating film; and
said method further comprising a step of processing a common unit in accordance with characteristics of a composite type thin film magnetic head to be manufactured,
whereby said step comprises:
the step of forming a magnetoresistive element along the surface of the first magnetic layer such that the magnetoresistive element extends in an electrically and magnetically isolated manner;
the step of forming a third magnetic layer which extends along said magnetoresistive element to constitute the other shield for the magnetoresistive type thin film magnetic head, and is coupled with said second magnetic layer formed within said recessed portion to constitute the remaining part of said one of poles for the inductive type thin film magnetic head;
the step of forming a write gap layer which extends along at least a surface of the third magnetic layer;
the step of forming a fourth magnetic layer along a surface of the write gap layer such that the fourth magnetic layer is opposed to said third magnetic layer and is magnetically coupled with said second magnetic layer at a rear position remote from the air bearing surface to constitute the other pole for the inductive type thin film magnetic head; and
the step of polishing the air bearing surface.
The present invention also relates to a common unit which can be commonly used for manufacturing composite type thin film magnetic heads having various characteristics in an efficient manner.
According to the invention, a common unit for composite type thin film magnetic head comprises:
a substrate having a recessed portion formed in a surface thereof;
a first magnetic layer constituting one of shields for a magnetoresistive type thin film magnetic head and extending along said surface of the substrate from an end surface constituting an air bearing surface to at least a vicinity of an edge of said recessed portion;
a second magnetic layer constituting a part of one of poles for an inductive type thin film magnetic head and extending over a part of an inner surface of the recessed portion such that the second magnetic layer is magnetically separated from the first magnetic layer; and
at least a part of a thin film coil of the inductive type thin film magnetic head formed within said recessed portion in an electrically isolated manner by an insulating layer.
The above mentioned composite type thin film magnetic head according to the present invention has a major difference from the known composite type thin film magnetic head in that one of poles for the inductive type thin film magnetic head is divided into the second magnetic layer and the third magnetic layer. The composite type thin film magnetic head according to this invention may be classified into a first basic structure in which a part of the thin film coil of the inductive type thin film magnetic head is formed within the recessed portion and the remaining part of the thin film coil is formed above the first mentioned thin film coil formed within the recessed portion, and a second basic structure in which the thin film coil of the inductive type thin film magnetic head is wholly formed within the recessed portion.
In the above first basic structure, a reference position of throat height zero of the inductive type thin film magnetic head is defined by an edge of an insulating layer supporting the thin film coil formed above the thin film coil provided within the recessed portion in an isolated manner by means of an insulating layer, and an apex angle is defined by an inclination angle of a side surface of the insulated layer.
In the above mentioned second basic structure, the reference position of throat height zero of the inductive type thin film magnetic head is defined by the edge of the recessed portion, and the apex angle is defined by an inclination angle of the side wall of the recessed portion. In this case, an inclination angle of the side wall of the recessed portion defining the apex angle may be preferably set to 45-75xc2x0, particularly 55-65xc2x0.
In the second basic structure, it is preferable that the surface of the first magnetic layer opposite to the substrate is coplanar with the surface of the insulating layer opposite to a bottom surface of the recessed portion, said insulating layer isolating the thin film coil formed within the recessed portion.
Moreover it is preferable to provide a non-magnetic layer on a surface of said insulating layer opposite to the bottom surface of the recessed portion such that a surface of said non-magnetic layer opposite to the substrate is coplanar with the surface of the third magnetic layer opposite to the substrate.
In the above structure, it is preferable that the write gap layer is formed to extend along the coplanar surfaces of said third magnetic layer and non-magnetic layer, and said fourth magnetic layer is formed to extend along the flat surface of the write gap layer. Such a flat surface can be easily manufactured to have a highly precise dimension.
Further, in the second basic structure, it is preferable that when it is predicted that a throat height which will be obtained with reference to a position of throat height zero defined by the edge of the recessed portion becomes longer than a desired value, a non-magnetic layer is provided above said recessed portion such that a surface of the non-magnetic layer is higher than that of the third magnetic layer and an edge of the non-magnetic layer projects toward the air bearing surface beyond the edge of the recessed portion, said write gap layer is extended from the surface of said third magnetic layer opposite to the substrate to the surface of the non-magnetic layer opposite to the substrate to include a step, and said forth magnetic layer is extended over the surface of the write gap layer to include a step corresponding said step of the write gap layer.
In the above explained structure, since the reference position of throat height zero is defined by the edge of the non-magnetic layer closer to the air bearing surface than the edge of the recessed portion, the throat height can be shortened. It should be noted that even in this case, the MR Height is not shortened and is remained at a desired value.
In the composite type thin film magnetic head according to this invention, the non-magnetic layer is preferably provided between the inner surface of the recessed portion and the second magnetic layer.
Furthermore, the first magnetic layer may be formed to extend over the side wall of the recessed portion beyond its edge.
Moreover, the second magnetic layer may be coupled with the third magnetic layer in various manner, e.g. the inner edges of these magnetic layers may be aligned with each other, or the inner edge of the third magnetic layer may be projected inwardly beyond the inner edge of the second magnetic layer. In the latter case, there can be obtained a margin in positioning these magnetic layers, but the reference position of throat height zero approaches closer to the inner side, the throat height is liable to be prolonged.
In the above mentioned first basic structure, the insulating layer supporting the thin film coil portion formed above the thin film coil portion formed within the recessed portion may be preferably projected from the surface of the third magnetic layer opposite to the substrate, said write gap layer may be provided to extend from the surface of the third magnetic layer opposite to the substrate to the surface of said insulating layer beyond a step, and said fourth magnetic layer may be extended along the write gap layer to include a step corresponding to said step.
In this case, it is preferable to project the edge of the insulating layer toward the air bearing surface beyond the edge of the recessed portion to shift the reference position of throat height zero closer to the air bearing surface than the edge of the recessed portion.
Moreover, in the composite type thin film magnetic head according to the invention, in order to suppress the leakage of the magnetic flux, a width of at least the pole portion of the third magnetic layer extending from the air bearing surface is preferably made substantially equal to that of the write gap layer. Furthermore, in order to suppress the leakage of the magnetic flux much more efficiently, it is preferable to provide the trim structure in the surface of the third magnetic layer opposite to the substrate, said trim structure having a width substantially equal to that of the pole portions of the write gap layer and fourth magnetic layer.
In the composite type thin film magnetic head according to the present invention, the third magnetic layer is preferably made of a material having a higher saturation magnetic flux density than that of the second magnetic layer. As stated above, in the composite type thin film magnetic head according to this invention, the bottom pole is divided into two portions, i.e. the second magnetic layer and the third magnetic layer. When the third magnetic layer constituting the pole chip is made of a material having a higher saturation magnetic flux density than the second magnetic layer, the assembly can be processed much more easily during the manufacture and the manufacturing cost can be reduced upon compared with a case in which the bottom pole is wholly made of a material having a high saturation magnetic flux density.
Moreover, in the method of manufacturing the composite type thin film magnetic head according to the invention, when the thin film is wholly formed within the recessed portion, the magnetoresistive element is formed after the formation of the thin film coil, and thus the magnetoresistive element is not subjected to the heating treatment for forming the thin film coil and the property of the magnetoresistive element is not degraded. Therefore, it is advantageously for manufacturing the GMR element which has a higher reading sensitivity, but is liable to be degraded by heat. It should be noted that the influence of heat to the magnetoresistive element can be still mitigated in the method according to the invention, in which a part of the thin film coil is formed within the recessed portion and the remaining portion of the thin film coil is formed after the formation of the magnetoresistive element.
In the method of manufacturing a composite type thin film magnetic head according to the invention, it is preferable that said steps of forming the recessed portion in the substrate and of forming the first magnetic layer include the step of forming the first magnetic layer serving as a mask having an opening corresponding to the recessed portion to be formed, and the step of forming the recessed portion in the surface of the substrate by performing an etching process while the first magnetic layer is used as a mask. In order to form precisely the deep recessed portion having a depth not less than 5 xcexcm, the first magnetic layer may be preferably formed by plating and the etching is performed by a reactive ion etching.
Furthermore, when all the thin film coil is formed within the recessed portion, by polishing the air bearing surface while the edge of the recessed portion is used as the positional reference, it is possible to obtain the inductive type thin film magnetic head, whose throat height is defined with respect to the edge of the recessed portion and whose apex angle is defined by an inclination angle of the side wall of the recessed portion. Since the position of the edge of the recessed portion does not change during the manufacturing process, the throat height and apex angle can be precisely formed to have desired values.
Moreover, in the manufacturing method according to this invention, it is preferable that after forming the thin film coil within the recessed portion, a first non-magnetic layer is formed on the insulating layer which isolates the thin film coil formed within the recessed portion, and at least said first non-magnetic layer is polished such that a surface of the first non-magnetic layer becomes coplanar with that of the first magnetic layer. Furthermore, it is preferable that after forming said magnetoresistive element and third magnetic layer, a second non-magnetic layer is formed on said first non-magnetic layer, and at least said second non-magnetic layer is polished such that a surface of the second non-magnetic layer becomes coplanar with that of the third magnetic layer.
It is further preferable that said write gap layer is formed to be flat on said coplanar surfaces of the third magnetic layer and second non-magnetic layer, and said fourth magnetic layer is formed to be flat on the flat surface of the write gap layer.
In the method of manufacturing a composite type thin film magnetic head according to the invention, it is preferable that a pole portion is formed by etching the write gap layer by means of a reactive ion etching while the pole portion of the third magnetic layer is used as a mask, and then the trim structure having a substantially equal width to that of the pole portions of the third magnetic layer and write gap layer is formed by etching the surface of the fourth magnetic layer by means of an ion beam etching while said pole portions are used as a mask.
By manufacturing the thin film magnetic head in this manner, a width of the fourth magnetic layer constituting the other pole becomes substantially equal to a width of the trim structure of the third magnetic layer constituting the pole chip. Therefore, the leakage of the magnetic flux between these magnetic layers can be suppressed and an effective track width can be narrowed to increase the surface recording density.
According to the invention, in the method of manufacturing and stocking a number of common units which can be commonly used for composite type thin film magnetic heads having various characteristics, it is preferable that when it is predicted that a throat height which will be obtained with reference to a position of throat height zero defined by the edge of the recessed portion becomes longer than a desired value although a MR height is equal to a desired value, after forming the third magnetic layer, a non-magnetic layer is formed above said recessed portion such that a surface of the non-magnetic layer is higher than that of the third magnetic layer and an edge of the non-magnetic layer projects toward the air bearing surface beyond the edge of the recessed portion, said write gap layer and fourth magnetic layer are formed on the surfaces of said third magnetic layer and non-magnetic layer to include a step, and the air bearing surface is polished while said edge of the non-magnetic layer is used as a positional reference.
According to the invention, when it is predicted that a desired NLTS characteristic could not be obtained by only the thin film coil formed within the recessed portion, it is desirable to form an additional thin film coil above the thin film coil provided within the recessed portion in such a manner that the additional thin film coil is isolated by an insulating layer.
Furthermore, when it is predicted that a throat height which will be obtained with reference to a position of throat height zero defined by the edge of the recessed portion becomes longer than a desired value although a MR height is equal to a desired value, said insulating layer supporting said additional thin film coil is formed such that a surface of the insulating layer is higher than that of the third magnetic layer and an edge of the non-magnetic layer projects toward the air bearing surface beyond the edge of the recessed portion, said write gap layer and fourth magnetic layer are formed on the surfaces of said third magnetic layer and insulating layer to include a step, and the air bearing surface is polished while said edge of the non-magnetic layer is used as a positional reference.
Moreover, in the common unit for a composite type thin film magnetic head according to this invention, it is preferable that the surfaces of the first magnetic layer, the end surface of the second magnetic layer and the surface of the non-magnetic layer are coplanar with each other.